Fuel cells are electrochemical devices which combine a fuel such as hydrogen and an oxidant such as oxygen to produce electricity. The term fuel cell is typically used to refer to either a single cell or a plurality of cells depending upon the context in which it is used. The plurality of cells is typically bundled together and arranged to form a stack with the plurality of cells commonly arranged in electrical series.
In order to mitigate against undesirable leakage of fluids from between the plates, a seal is often used. The seal is disposed along a peripheral edge of the plates, and/or around a periphery of an aperture extending through the plates. The seal may include an elastomeric seal, or alternatively, the metal plates may be formed to define a raised bead seal. The raised bead may be formed on a planar metal sheet adjacent an outer edge of the sheet, or adjacent an edge surrounding an aperture formed in the sheet. The raised bead may be formed in the metal sheet by a stamping operation, although other methods may be used. The raised bead seal may be substantially symmetrical about a longitudinal center line of the raised bead seal. However, it should be appreciated that the raised bead seal may be non-symmetrical about the longitudinal center line. The raised bead seal may include a generally arcuate cross sectional shape perpendicular to the longitudinal center line. The generally arcuate cross sectional shape of the raised bead seal provides an elastic response to a load in a direction normal to the planar metal sheet.
The raised bead seal may be compressed against an adjoining plate to form a seal against the adjoining plate. If portions of the raised bead seal have a high stiffness, and others have a lower stiffness, the high stiffness areas of the raised bead seal may prevent the lower stiffness areas of the raised bead seal from forming a tight seal. Accordingly, the raised bead seals should have a uniform stiffness in all sections of the raised bead seal in order to form a tight seal around the entire peripheral edge of the plates and/or around the entire periphery of the adjacent aperture.
Sealing beads may militate against fluid leakage from adjacent plates within a fuel cell stack and facilitate flow of reactants within the fuel cell stack. Under extreme loads, for example a vehicle crash, the bead may become over-compressed and lead to leaking within a fuel cell or failure of the fuel cell stack. In particular, sealing beads may corners which may experience high contact pressure. Inclusion of connections at the corners of beads may reduce contact pressure.